Perceptual, developmental, experiential, and physiological parameters of swimming in Melanopline grasshoppers (Orthoptera: Acrididae)

Abstract

The roles of perception, development, experience, and physiology on the swimming behavior of grasshoppers in an arena were investigated usingMelanoplus bivittatus, M. differentialis, andM. sanguinipes. The parameters of swimming included capacity (the ability to reach the edge of a 45-cm-diameter water basin within 3 min), net displacement time (time required to reach the edge of the arena), and orientation (ability to make initial contact with a “target” pattern).Melanoplus sanguinipes adults were most attracted to a vertical rectangle set at 90° to the water surface (the standard target). Orientation ability decreased significantly as the target became square or it declined to 60°, and there was virtually no orientation to horizontal patterns or those at ≤45°. All nymphal instars ofM. sanguinipes exhibited the capacity to swim and orient to a standard target. Although the net displacement time was lowest from the third instar through the adult stages, the earlier instars (first through fourth) had the greatest relative net displacement rates. As adults aged, their net displacement time and orientation ability declined significantly, particularly in males. BothM. differentialis andM. sanguinipes adults showed a decline in net displacement time over a 10-day trial period. The loss of a hind leg did not significantly alter swimming performance of eitherM. bivittatus orM. sanguinipes adults, but this alteration significantly reduced the net displacement time ofM. differentialis. DecerebratedM. differentialis adults were capable of swimming for several minutes.